Failsafe Brake Valve Unit for Fast Parking Brake Engagement
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Solution Overview
Problem
Modern electronically controllable pneumatic brake systems in utility vehicles face challenges in providing immediate and reliable failsafe braking operations, particularly due to time delays and pressure offsets in engaging the parking brake during system faults, which compromise the sustained braked state of the vehicle.
Innovation Solution
A fail-safety valve unit with a monostable failsafe brake valve, connected to a separate actuation branch, ensures failsafe braking by pneumatically linking the main port to the parking brake function, utilizing redundant compressed-air sources to maintain the braked state even in the event of leaks or failures, and includes a selector valve to switch between independent air sources for redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the parking brake is activated to provide failsafe braking in the event of a fault, then the brake system can continue to be operated with limitations, but there is a time delay due to dead time in the response behavior and pressure offset that must be overcome
Solution Approach 1:
The fail-safety valve unit is pre-configured with a monostable failsafe brake valve that automatically activates upon detection of a fault condition. The valve is designed to immediately connect the main port to the failsafe brake port when activated, eliminating the need to overcome pressure offsets that would otherwise delay parking brake engagement. This preliminary configuration enables immediate failsafe braking operation without the time delay associated with traditional parking brake activation sequences.
2Reliability
If a bypass valve is used to transmit control pressures in the event of subsystem failure, then pneumatic supply to the failed circuit is provided, but the system lacks sustained assurance of the braked state
Solution Approach 1:
The fail-safety valve unit acts as an intermediary component that receives control pressures from the parking brake function and directly transmits them to the failsafe brake port through the monostable valve. This intermediary mechanism ensures that once activated, the failsafe brake pressure is sustained without dependency on the original control circuit, maintaining the braked state even if the primary control system fails or experiences leaks.
3Reliability
If the failsafe brake valve is configured as a monostable valve that opens in the event of electrical failure, then failsafe braking operation is initiated, but the system requires additional valve components
Solution Approach 1:
The monostable failsafe brake valve is designed to automatically activate in response to electrical failure without requiring external intervention or complex control logic. When the control signal is lost or a fault is detected, the valve's inherent monostable mechanism causes it to switch to the open position, immediately establishing the failsafe brake pressure connection. This self-service capability simplifies the overall control system while ensuring reliable failsafe operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures reliable and sustained failsafe braking by engaging the parking brake, maintaining vehicle deceleration, and enhancing system redundancy, thereby improving safety and reliability in autonomous driving scenarios.
Implementation Method 1
a failsafe brake valve (40) which is configured as a monostable valve and which is controllable by the control unit (410) or by an external control unit (418) and which is configured to pneumatically connect the main port (20) and the failsafe brake port (22) when in an open position (40A) in order to output a failsafe brake pressure (pN) at the failsafe brake port (22)
Data Source
AI summary
A fail-safety valve unit of an electronically controllable pneumatic brake system for a vehicle is disclosed. The unit includes a main port for providing a first pressure, a failsafe brake port, and a failsafe brake valve. The brake valve is controllable by a control unit. The brake valve pneumatically connects the main port and the failsafe brake port when in an open position to output a failsafe brake pressure at the failsafe brake port. In the event of a fault, an electrical failure, and/or a diagnostic event of the control unit, the brake valve is in the open position and a failsafe braking operation of the vehicle is initiated through a failsafe brake pressure at the failsafe brake port by the brake system. The main port is pneumatically connected to a parking brake function to receive an output parking brake pressure or a pressure derived therefrom, as the first pressure.